Exogenous Immunosuppression Research Articles

ATP6V0A1-dependent cholesterol absorption in colorectal cancer cells triggers immunosuppressive signaling to inactivate memory CD8+ T cells

Obesity shapes anti-tumor immunity through lipid metabolism; however, the mechanisms underlying how colorectal cancer (CRC) cells utilize lipids to suppress anti-tumor immunity remain unclear. Here, we show that tumor cell-intrinsic ATP6V0A1 drives exogenous cholesterol-induced immunosuppression in CRC. ATP6V0A1 facilitates cholesterol absorption in CRC cells through RAB guanine nucleotide exchange factor 1 (RABGEF1)-dependent endosome maturation, leading to cholesterol accumulation within the endoplasmic reticulum and elevated production of 24-hydroxycholesterol (24-OHC). ATP6V0A1-induced 24-OHC upregulates TGF-β1 by activating the liver X receptor (LXR) signaling. Subsequently, the release of TGF-β1 into the tumor microenvironment by CRC cells activates the SMAD3 pathway in memory CD8+ T cells, ultimately suppressing their anti-tumor activities. Moreover, we identify daclatasvir, a clinically used anti-hepatitis C virus (HCV) drug, as an ATP6V0A1 inhibitor that can effectively enhance the memory CD8+ T cell activity and suppress tumor growth in CRC. These findings shed light on the potential for ATP6V0A1-targeted immunotherapy in CRC.

Cytomegalovirus reactivation with high viral load in a patient of coronavirus disease 2019 acute respiratory distress syndrome: a case report

IntroductionCytomegalovirus establishes life-long latency after primary infection in childhood. Cytomegalovirus reactivation has been well reported in immune-compromised patients; however, in the last few years it has been observed that cytomegalovirus reactivation also occurs in critically ill patients without exogenous immunosuppression, which increases length of intensive care unit stay and mortality rate.Case reportA 63-year-old Indian male, without any known comorbidity, developed severe coronavirus disease 2019 and was admitted to the intensive care unit. He received remdesivir, tocilizumab, steroids, anticoagulants, and empiric antibiotics over the next 3 weeks. However, his clinical condition did not improve much, and during the 9th week of illness his condition started deteriorating and routine bacterial cultures, fungal cultures, and cytomegalovirus real-time polymerase chain reaction on blood were negative. His clinical condition worsened rapidly, which led to the need for invasive mechanical ventilation. Tracheal aspirate bacterial and fungal culture showed no growth, but cytomegalovirus real-time polymerase chain reaction showed 21,86,000 copies/mL in tracheal aspirates. After 4 weeks of ganciclovir treatment, the patient improved clinically and was discharged. Currently he is doing well and able to do his routine activity without the need of oxygen.ConclusionTimely management with ganciclovir is associated with favorable outcome in cytomegalovirus infection. Thus, it can be suggested that treatment should be initiated with ganciclovir if a patient with coronavirus disease 2019 has high cytomegalovirus load in tracheal aspirates, along with unexplained and prolonged clinical and/or radiological features.

Dominant regulation of long-term allograft survival is mediated by microRNA-142.

Organ transplantation is often lifesaving, but the long-term deleterious effects of combinatorial immunosuppression regimens and allograft failure cause significant morbidity and mortality. Long-term graft survival in the absence of continuing immunosuppression, defined as operational tolerance, has never been described in the context of multiple major histocompatibility complex (MHC) mismatches. Here, we show that miR-142 deficiency leads to indefinite allograft survival in a fully MHC mismatched murine cardiac transplant model in the absence of exogenous immunosuppression. We demonstrate that the cause of indefinite allograft survival in the absence of miR-142 maps specifically to the T cell compartment. Of therapeutic relevance, temporal deletion of miR-142 in adult mice prior to transplantation of a fully MHC mismatched skin allograft resulted in prolonged allograft survival. Mechanistically, miR-142 directly targets Tgfbr1 for repression in regulatory T cells (TREG ). This leads to increased TREG sensitivity to transforming growth factor - beta and promotes transplant tolerance via an augmented peripheral TREG response in the absence of miR-142. These data identify manipulation of miR-142 as a promising approach for the induction of tolerance in human transplantation.

Targeted deletion of Traf2 allows immunosuppression-free islet allograft survival in mice.

Administration of anti-CD40 ligand (CD40L) antibodies has been reported to allow long-term islet allograft survival in non-human primates without the need for exogenous immunosuppression. However, the use of anti-CD40L antibodies was associated with thromboembolic complications. Targeting downstream intracellular components shared between CD40 and other TNF family co-stimulatory molecules could bypass these complications. TNF receptor associated factor 2 (TRAF2) integrates multiple TNF receptor family signalling pathways that are critical for T cell activation and may be a central node of alloimmune responses. T cell-specific Traf2-deficient mice (Traf2TKO) were generated to define the role of TRAF2 in CD4+ T cell effector responses that mediate islet allograft rejection in vivo. In vitro allograft responses were tested using mixed lymphocyte reactions and analysis of IFN-γ and granzyme B effector molecule expression. T cell function was assessed using anti-CD3/CD28-mediated proliferation and T cell polarisation studies. Traf2TKO mice exhibited permanent survival of full MHC-mismatched pancreatic islet allografts without exogenous immunosuppression. Traf2TKO CD4+ T cells exhibited reduced proliferation, activation and acquisition of effector function following T cell receptor stimulation; however, both Traf2TKO CD4+ and CD8+ T cells exhibited impaired alloantigen-mediated proliferation and acquisition of effector function. In polarisation studies, Traf2TKO CD4+ T cells preferentially converted to a T helper (Th)2 phenotype, but exhibited impaired Th17 differentiation. Without TRAF2, thymocytes exhibited dysregulated TNF-mediated induction of c-Jun N-terminal kinase (JNK) and canonical NFκB pathways. Critically, targeting TRAF2 in T cells did not impair the acute phase of CD8-dependent viral immunity. These data highlight a specific requirement for a TRAF2-NFκB and TRAF2-JNK signalling cascade in T cell activation and effector function in rejecting islet allografts. Targeting TRAF2 may be useful as a therapeutic approach for immunosuppression-free islet allograft survival that avoids the thromboembolic complications associated with the use of anti-CD40L antibodies.

CD3 T-Cell Infiltrates at Diagnosis Predicts Overall Survival in Solid Organ Transplant Recipients with Post-Transplant Lymphoproliferative Disorders (PTLD)

IntroductionThe host immune status is central to both the pathogenesis and treatment of Post-Transplant Lymphoproliferative Disorders. (PTLD) The most commonly used prognostic model for PTLD, the International Prognostic Index (IPI), currently does not account for the effect of immune status on patient outcomes. We hypothesize that CD3 positive T-cell infiltrate density in the tumor microenvironment, thought to be a surrogate of the potency of the host versus tumor immune response, may be prognostic of overall survival in PTLD.MethodsA database consisting of 131 biopsy confirmed PTLD cases occurring in pediatric and adult solid organ transplant recipients after the year 2000 in Alberta, Canada was analyzed for clinical prognostic variables and overall survival. CD3 infiltrate was determined by a blinded pathologist (JZ) using a standardized integer scoring system (0 - 3) to quantify CD3-positive cells in archived, formalin-fixed paraffin embedded tissue stained by immunohistochemistry. Tissue was available and assessed on a total of 72 patients. Survival analysis was done by Cox regression, with between group differences tested by a Pearson’s chi-square test, with p < 0.05 being taken as significant.ResultsMedian age at diagnosis was 40.2 years. Histology subtypes included early (n = 7), polymorphic (n = 17), monomorphic, (n = 100) Hodgkin, (n = 8) and unavailable. (n = 2) Immune suppression regimens at diagnosis included tacrolimus + mycophenolate (n = 29), tacrolimus + azathioprine (n = 11), cyclosporine + mycophenolate (n = 14), cyclosporine + azathioprine (n = 4), single agent tacrolimus (n = 11), single agent cyclosporine (n = 2), and other immunosuppressive regimens. (n = 4)A denser CD3 T-cell infiltrate, defined as a CD3 score of 2-3, had a statistically significant protective effect by univariate Cox regression with respect to overall survival. (HR 0.352, p = 0.008) A CD3 score of 2-3 was negatively associated with a monomorphic histology (p < 0.001), but was not statistically associated with lymphocyte count, early PTLD, EBV status or bone marrow involvement. In the diffuse large B-cell type PTLD subgroup (n = 61) the association of a dense CD3 T-cell infiltrate with an improved OS was preserved. (HR 0.276, p = 0.041)Clinical factors identified as significant by univariate Cox regression with respect to overall survival included age < 18 (HR = 0.380, p = 0.010), monomorphic histology (HR = 2.287, p = 0.02), IPI 3-5 (HR = 3.697, p < 0.001), BM involvement (HR 2.437, p = 0.008), and lymphocyte count < 1.0. (HR 2.449, p = 0.001) Clinical factors deemed to not be significant with respect to overall survival by univariate Cox regression included CD20 (p = 0.730), thoracic transplant organ (p = 0.314), PTLD onset within 1 year of transplant (p = 0.763), allograft involvement (p = 0.253), albumin of < 30 (p = 0.062) and tumor EBV status. (p = 0.278)Multivariate Cox regression with respect to overall survival, including monomorphic histology, IPI 3-5, lymphocyte count < 1.0 and CD3 score of 2-3 again showed a statistically significant protective effect of a higher CD3 score. (HR 0.307, p = 0.022) No other clinical variables reached significance in the multivariate analysis.ConclusionsA dense CD3 T-cell infiltrate in the tumor microenvironment at diagnosis is protective with regards to overall survival in PTLD by both univariate and multivariate Cox regression, versus traditional clinical prognostic markers. This is reflective of the prognostic importance of the host immune response, which can be altered by changes in exogenous immunosuppression. In the future, validated histologic measures of immune status such as the CD3 score may be integrated into existing models, such as the IPI, to provide additional prognostic power in PTLD. [Display omitted] [Display omitted] [Display omitted] DisclosuresOwen:Janssen: Honoraria; Gilead: Honoraria, Research Funding; Pharmacyclics: Research Funding; Celgene: Honoraria, Research Funding; Abbvie: Honoraria; Lundbeck: Honoraria, Research Funding; Novartis: Honoraria; Roche: Honoraria, Research Funding.

Cryptosporidiosis Treated With Nitazoxanide in Intestinal Transplantation

In developed countries, infections with Cryptosporidium species are rare and are often associated with waterborne or food-borne outbreaks. There is increasing evidence that solid organ transplant recipients are at increased risk of debilitating cryptosporidiosis in the setting of exogenous immunosuppression. We report a case of cryptosporidiosis, likely acquired through travel, in an intestinal transplant recipient who was successfully treated with nitazoxanide. This case highlights the unique challenges in diagnosis and treatment of immunocompromised patients with cryptosporidiosis, specifically in intestinal transplantation.

Loss of TRAF2 Impairs Alloreactive CD4+ T Cells and Maintains Tregs to Favour Islet Allograft Survival Without Exogenous Immunosuppression.

The signaling molecule, TNF-receptor associated factor 2 (TRAF2) integrates multiple TNF-family signaling pathways critical for T cell activation suggesting TRAF2 may be a potential target for promoting allograft survival.Here, the role of TRAF2 in T cell responses towards allografts is examined using T cell specific TRAF2-deficient mice (TRAF2TKO). TRAF2TKO mice permanently accepted the majority of full MHC-mismatched islet allografts and display delayed rejection of vascular heterotopic heart and skin allografts without exogenous immunosuppression. Further, TRAF2TKO failed to proliferate in an in vitro MLR - thus TRAF2 deficiency impairs the alloimmune response. Loss of TRAF2 resulted in diminished CD4+ T cell activation as shown by reduced proliferation and decreased expression of activation markers CD44 and CD25 and effector molecules granzyme B and IFN-gamma in response to alloantigen. Further, under Th1 polarizing conditions, TRAF2TKO CD4+ T cells showed abnormal expression of the Th2 cytokine IL-13. Furthermore, TRAF2TKO CD4+ T cells more readily converted to a Treg phenotype in the presence of TGF-beta; and in vivo TRAF2TKO mice harbored increased Tregs. TRAF2 deficiency delayed activation of TNF-induced JNK and NF-kB in T cells. Therefore TRAF2 coordinates extracellular signals from TNF-family ligands to maintain T cell lineage selection and effector function.

Travel Medicine and Transplant Tourism in Solid Organ Transplantation

Travel Medicine and Transplant Tourism in Solid Organ Transplantation

Mycobacterium tuberculosis Infections in Solid Organ Transplantation

Mycobacterium tuberculosis Infections in Solid Organ Transplantation

Vaccination of patients with inflammatory bowel disease: Practical recommendations

Patients with inflammatory bowel disease (IBD) have a greater risk of infection associated with the endogenous immunosuppression brought about by their underlying disease as well as the exogenous immunosuppression resulting from their therapies. In the last few years guidelines and consensus papers have been issued on the indication of vaccines for these patients as primary prevention of infection. However, vaccine coverage is low, likely because the risk for infection and both safety and efficacy concerns regarding vaccines are scarcely perceived in such cases. The available scientific evidence shows that immunization is safe for most preparations, and bears no association with an increased risk for disease activity. This paper reviews the available scientific literature, and provides recommendations on the vaccination of adults with IBD.

Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is an opportunistic viral infection of the human CNS that has gained new importance because of AIDS and newer immunosuppressive therapies. It destroys oligodendrocytes, leading to neurologic deficits associated with demyelination. PML most commonly occurs in patients who are HIV infected, but increasing numbers of patients are being recognized in the context of immunosuppressive therapies for autoimmune diseases. The precise pathogenesis of infection by JC virus, the etiologic human papovavirus, remains elusive, but much has been learned since the original description of the pathologic entity PML in 1958. Detection and diagnosis of this disorder have become more sophisticated with MRI of the brain and spinal fluid analysis using PCR detection. Immune reconstitution inflammatory syndrome complicates reversal of immunosuppression when PML has established a foothold in the brain. No effective therapy exists, but there is hope for better management of patients by withdrawing exogenous immunosuppression and reconstituting the immune system, with a projection of better long-term survival.

Editorial Commentary: Understanding Risk and Enhancing Safety in Immunotherapy Trials

these patients for herpesvirus infections has provided novel insights into the effects of common viral infections with the use of potent exogenous immunosuppression in the nontransplant setting. In the current study, the authors performed careful laboratory and clinical monitoring for Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus (HSV), and varicella zoster virus (VZV). Both primary infections and reactivations were observed but significantly increased morbidity was not seen in patients receiving either one or both immunosuppressive drugs compared with placebo. There was a trend toward greater EBV viral burden (P= .06) in patients receiving both daclizumab and MMF compared to those on no immunosuppression. However, most patients were either asymptomatic or had a self-limited mononucleosis-like syndrome. EBV is an important herpesvirus in transplantation; pediatric transplant patients especially are at greater risk of posttransplant lymphoproliferative disease (PTLD), primarily because they are often EBV-seronegative prior to transplantation and may receive a seropositive organ. In this study, EBV viral loads were reportedly not significantly different from viral loads measured in transplant patients at the same lab. In the transplant setting, high EBV viral loads have been correlated with an increased risk of PTLD [3]; however, other

Sepsis and Therapeutic Hypercapnia

Sepsis and Therapeutic Hypercapnia

Mycobacterium tuberculosis in Solid Organ Transplant Recipients

Mycobacterium tuberculosis in Solid Organ Transplant Recipients

Progressive multifocal leukoencephalopathy

Treatment of progressive multifocal leukoencephalopathy (PML) in a patient with exogenous immunosuppression starts with discontinuation of immunosuppressive medication. The restored host immunity will clear JC virus, the cause of PML, from the brain via cell-mediated immune mechanisms. Patients with solid-organ transplants will lose the transplanted organ, however, and patients who have autoimmune disorders may experience exacerbation of their underlying disease. These factors need to be weighed against the potentially fatal nature of PML. If the patient's immunosuppression is AIDS-related, highly active antiretroviral therapy (HAART) should be initiated if it has not previously been used. If the patient is already receiving HAART, the therapy should be changed to optimize treatment, with the goals of a nondetectable HIV viral load and normalization or near normalization of the CD4 count. For non-AIDS PML patients, daily intravenous cytosine arabinoside for 5 days can be offered if the patient is not pancytopenic and can tolerate a chemotherapeutic agent. For AIDS patients with PML or failing non-AIDS patients with neurologic deterioration, cidofovir can be considered. These therapies can be offered if neurologic stabilization satisfies the quality-of-life goals for the patient. For patients intolerant of other therapies or unsuited to them, oral mirtazapine or risperidone can be considered. The safety of these agents has been established in the treatment of psychiatric disease, but their efficacy has not yet been proven. Small interfering RNA (siRNA) therapy holds the promise of specific antiviral therapy, but delivery methods, safety, and efficacy are yet to be established.

Spontaneous Operational Tolerance After Immunosuppressive Drug Withdrawal in Clinical Renal Allotransplantation

Tolerance is the so-called "Holy Grail" of transplantation, but achieving this state is proving a major challenge, particularly in the clinical setting. Even in rodents, the definition of true transplant tolerance is not applicable to many models, with late graft damage often occurring despite long-term graft survival. Hence the term "operational tolerance," based more on graft function and absence of exogenous immunosuppression, is being adopted. Although the most sought-after goal in this field is to intentionally induce this state in a controlled manner, translating protocols across species from rodents to the clinic, the current literature demonstrates that this is proving a formidable task. A complementary approach is to address transplant tolerance from a different angle, by studying tolerance-like phenomena that occur "unintentionally" in transplant patients after immunosuppressive drug weaning. Such spontaneous operational tolerance, which can take place after years of immunosuppression, is rare in kidney transplant recipients. However, determining exactly how this state arises and how it can be detected may make it possible to induce it in a greater number of patients and then to return to the drawing board to rationally design protocols that have a greater chance of clinical success. Moreover, the study of such patients should help in the identification of biomarkers of low immunological risk that could be used to select patients for potential weaning. Collaborative efforts through international networks, together with the application of newer and more powerful technologies to diagnostic, prognostic, and mechanistic research, may help transplanters to achieve this goal.

Fulminant Mulch Pneumonitis: An Emergency Presentation of Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is associated with multiple and recurrent infections. In patients with CGD, invasive pulmonary infection with Aspergillus species remains the greatest cause of mortality and is typically insidious in onset. Acute fulminant presentations of fungal pneumonia are catastrophic. Case records, radiograph findings, and microbiologic examination findings of patients with CGD who had acute presentations of dyspnea and diffuse pulmonary infiltrates caused by invasive fungal infection were reviewed and excerpted onto a standard format. From 1991 through 2004, 9 patients who either were known to have CGD or who received a subsequent diagnosis of CGD presented with fever and new onset dyspnea. Eight patients were hypoxic at presentation; bilateral pulmonary infiltrates were noted at presentation in 6 patients and developed within 2 days after initial symptoms in 2 patients. All patients received diagnoses of invasive filamentous fungi; 4 patients had specimens that also grew Streptomyces species on culture. All patients had been exposed to aerosolized mulch or organic material 1-10 days prior to the onset of symptoms. Cases did not occur in the winter. Five patients died. Two patients, 14 years of age and 23 years of age, who had no antecedent history of recognized immunodeficiency, were found to have p47(phox)-deficient CGD. Acute fulminant invasive fungal pneumonia in the absence of exogenous immunosuppression is a medical emergency that is highly associated with CGD. Correct diagnosis has important implications for immediate therapy, genetic counseling, and subsequent prophylaxis.

Avenues for immunomodulation and graft protection by gene therapy in transplantation

Organ transplantation represents the only definitive therapy for many causes of end-organ failure. However, the universal success of this therapy is limited by chronic allograft rejection, the side effects of chronic immunosuppressive therapy, and a severe shortage of donor organs. Presently, the success of solid-organ transplantation depends on the continuous administration of toxic and nonspecific immunosuppressive agents, therapies that present risks for opportunistic infection, malignancy, and a variety of agent-specific side effects. To promote the use of transplantation with limited risk of long-term sequelae, three dominant research challenges emerge: (i) elimination of the need for exogenous immunosuppression by immunological tolerance induction; (ii) prevention of chronic rejection/graft dysfunction; and (iii) expansion of available organs for transplantation. Gene therapy may provide significant advances and solutions in each of these areas. Rejection of the graft in the immediate post-transplant period has been attacked through the transfer of immunomodulatory molecules in addition to tolerance inducing approaches. Chronic graft rejection may be similarly addressed through permanent tolerance induction or alternatively through the introduction of molecules to resist chronic graft damage. Genetic manipulation of stem cells may ultimately produce transgenic animals to serve as tissue donors to overcome the limited donor organ supply. This review will highlight ongoing developments in the translation of gene therapy approaches to the challenges inherent in transplantation.

Immunological Unresponsiveness in Chimeric Miniature Swine following MHC-Mismatched Spleen Transplantation

In rodents, spleen allotransplantation (SpTx) induces tolerance. We investigated the induction of chimerism and donor-specific unresponsiveness following pig SpTx. Thirteen pigs underwent splenectomy (day 0); all received a blood transfusion. In 11/13 pigs, SpTx was performed across a MHC class I (n=1) or full (n=10) barrier; two control pigs received no SpTx. All pigs were monitored for chimerism, and anti-donor immune responses, including suppressor assays. Four pigs (two asplenic controls and two with SpTx) underwent delayed donor-matched kidney transplantation without immunosuppression. Six of the 11 spleen grafts were lost from rejection (n=5) or splenic vein thrombosis (n=1), and five remained viable. All 11 SpTx recipients developed multilineage chimerism, but chimerism was rapidly lost if the graft failed. Two control pigs showed <6% blood chimerism for 4 and 11 days only. Pigs with functioning spleen grafts had multilineage chimerism in blood, thymus and bone marrow for at least 2-6 months, without graft-versus-host disease. These pigs developed in vitro donor-specific hyporesponsiveness and suppression. In 2 pigs tolerant to the spleen graft, donor MHC-matched kidney grafts survived for >4 and >7 months in the absence of exogenous immunosuppression; in two asplenic pigs, kidney grafts were rejected on days 4 and 15. Successful SpTx can result in hematopoietic cell engraftment and in vitro donor-specific unresponsiveness, enabling prolonged survival of subsequent donor-matched kidney grafts without immunosuppression.

Specific tolerance induction of allo-K b-skin grafts by FK506 in the CD8-depleted H-2 k recipients required low amounts of K b-antigen

MHC class I allo-grafts can be directly rejected by recipient CD8 T cells and be indirectly rejected by recipient CD4 T cells. Although the experimental results using the bm mutant and C57BL/6 mice indicated that CD4-mediated rejection of class I-disparate grafts is a relatively weak process and is expected to be more sensitive to additional exogenous immunosuppression, it is unclear that whether this mechanism can be used for inducing a specific tolerance of class I disparate grafts. In this study, we hypothesize that a short course of FK506 may induce a specific tolerance of class I-disparate skin grafts in the CD8-depleted recipients. K b-transgenic C3H mice, Tg.H-2 K b-1 and Tg.H-2 K b-2 mice that express high copies and low copies of K b-antigen respectively were used as donors. Wild type C3H mice (H-2 k) in which either CD4 or CD8 T cells were depleted by administration of anti-CD4 or CD8 monoclonal antibody (mAb) were used as recipients. Results showed that FK506 promoted longer survival of allo-K b skin grafts in CD8-depleted C3H mice than in CD4-depleted C3H mice. Graft survival from Tg.H-2 K b-2 mice was significantly longer than Tg.H-2 K b-1 mice. A short course of FK506 induced long-term survival of skin grafts from Tg.H-2K b-2 mice, but not from Tg.H-2K b-1 mice in CD8-depleted C3H recipients, even after FK506 was stopped. These mice also accepted grafts of Tg.H-2K b-1 mice when challenged with skin grafts from Tg.H-2K b-1 mice, but promptly rejected third party skin grafts from BALB/c (H-2 d) mice. T cells from K b-tolerant C3H mice did not respond to allo-K b-antigen in in vitro assays of mixed lymphocyte culture and cell-mediated cytotoxicity. In conclusion we found that a short course of FK506 treatment and low amounts of K b-antigen induced a K b-specific tolerance in the CD8-depleted recipients, and this tolerance maintained even after withdrawing the anti-CD8 mAb treatment.